I am the go-to guy for fixing others PCs.
In the beginning, about 8 years ago, I would be presented with a PC that wouldn't boot or, after boot, would perform very strangely. Maybe 50% of these problems were malware-related caused by allowing teenager access.
Starting about 4 years ago, there was a rash of requests to help set up WiFi networking and rootkit malware.
More recently, its settled into three primary categories, slow PC due to tons of anchor-laden startup programs, usage-questions about new software GUI versus old versions (Office 2007, Vista, &c) and problems associated with AVG software after attempting to uninstall.
Of course, most of the requests come to me over the phone with the expectation (hope, really) that I can somehow divine and resolve their vague and nebulously described problem while on the phone. While I can some of the time, most of the time I end the 30 minute frustrating call with, "I'll need to have direct hands-on access to the PC before I can analyze the real problem."